The present invention relates to a chemical analyzing apparatus, and more particularly to a colorimetric photometering apparatus utilizing a plurality of optical filters having different transmission spectrum ranges.
FIG. 1 is a schematic view showing an outline of a known photoelectric colorimetering analyzer. In FIG. 1, sample vessels 2 are transported successively into a position A by means of a snake chain 1 and a given amount of a sample contained in a sample vessel 2 situated at the position A is sucked into a nozzle 4 of a syringe 3. Then, the sucked sample is delivered into a reaction vessel 5. While the reaction vessel 5 is transported along a reaction line, at positions B and C, a first reagent 8 and a second reagent 9 are delivered into the reaction vessel 5 by syringes 6 and 8, respectively to form a test liquid. When the reaction vessel 5 reaches a position D, the test solution in the reaction vessel 5 is photometered photoelectrically by a colorimeter 14 comprising a rotary disc 10 for holding a plurality of optical filters .lambda..sub.1, .lambda..sub.2, . . . , .lambda.n along its periphery, a stepping motor 11 for rotating the disc 10, a light source 12, and a photoelectric converting element 13 such as a photomultiplier. The filters .lambda..sub.1, .lambda..sub.2, . . . , .lambda.n have different transmission spectrum ranges corresponding to test items to be effected.
In multi-item colorimetering, usually it is necessary to use a light beam having a spectrum range most suitable for a desired test item and therefore, any desired optical filter must be selected by rotating the disc 10 having a plurality of the optical filters .lambda..sub.1, .lambda..sub.2, . . . , .lambda.n by means of the stepping motor 11.
Disadvantages of the known photoelectric colorimeter mentioned above which is so constructed that the optical filter is selected mechanically are as follows.
(1) Since selection of the optical filter is effected by a mechanically driving mechanism, a relatively long time is required so that the processing time becomes longer. PA0 (2) Since a large size driving mechanism for selecting the optical filter is required, the whole colorimeter is made large in size. PA0 (3) In case of performing a two wavelength photometering which uses two optical filters having different spectrum ranges, since it is necessary to rotate the filter disc twice, a longer time is required than one wavelength photometering. PA0 (4) Since it is necessary to insert the optical filter into an optical path correctly, the driving mechanism needs high precision. PA0 (5) In order to effect a positioning described in (4), it is necessary to make diameters of the optical filters much larger than that necessary, and therefore the number of optical filters arranged on the rotary disc is limited.